Nipponosaurus

Nipponosaurus (meaning "Japanese lizard") is a lambeosaurine hadrosaur from sediments of the Yezo Group, in Sinegorsk on the island of Sakhalin, which was part of Japan at the time of the species' classification. The type and only species is N. sachalinensis, known only from a single juvenile specimen discovered in 1934 and named in 1936, by Takumi Nagao, with further material of the same individual found in 1937. Since then, the taxon has been largely ignored, and its validity has been doubted, with synonymy with other Asian hadrosaurs or status as a nomen dubium being suggested. Redescriptions from 2004 and 2017, however, have supported recognition as a distinct species. Dating the only specimen has been difficult, but based on associated mollusc taxa, the species likely lived sometime in the upper Santonian or lower Campanian, around 80 million years ago. The holotype (UHR 6590, University of Hokkaidō Registration) was discovered in November 1934 during the construction of a hospital for the Kawakami colliery of the Mitsui Mining Company on Karafuto Prefecture (now Sinegorsk, Sakhalin, Russia). It was disarticulated when discovered. N. sachalinensis was named and described in 1936 by Professor Takumi Nagao of the Imperial University of Hokkaido. The generic name refers to Nippon, the Japanese name of Japan; it was the first dinosaur named based on a find made on Japanese territory – though South Sakhalin was annexed by the Soviet Union in 1945. The specific name refers to Sakhalin. Although being relatively complete at the time of discovery, the specimen was missing much of the skull and limbs. A second expedition was organised in the summer of 1937, in which limb material pertaining to the holotype was recovered. The next year, Nagao authored a second article on the species describing these additional remains. Nipponosaurus was described as a member of the Trachodontidae; however Trachodon is now considered an invalid nomen dubium. The family is now known as the Hadrosauridae.